The demands of semiconductor manufacture have required the use of high performance surfactants and wetting agents in photoresist developer formulations. As line features shrink to smaller sizes and photoresist substrate materials become more aliphatic in nature (i.e. having lower surface energy), aqueous developer solutions are being formulated with surface tension reducing agents. Another requirement for these developers is that they have a low tendency to foam. This is accentuated by the movement toward larger wafer sizes. Low foam formation is particularly important when using spray-puddle techniques because microbubble entrainment during spreading of the solution over the photoresist surface can lead to defects. Surfactants that have been used in the past to increase wetting of the photoresist typically lead to higher foam formation. For the most part the industry has focused on the effect of surfactant on photoresist performance, such as contrast, critical dimension, and feature sharpness. Although the cleaning ability of underlying substrates is enhanced by typical surfactants, foam formation still remains a problem.
Tetramethylammonium hydroxide (TMAH) is the chemical of choice in aqueous alkaline solutions for developing photoresists according to Microlithography, Science and Technology, edited by J. R. Sheats and B. W. Smith, Marcel Dekker, Inc., 1998, pp 551-553. Surfactants are added to the aqueous TMAH solutions to reduce development time and scumming and to improve surface wetting.
U.S. Pat. No. 5,939,476 discloses the use of alkylated polyamines for reducing equilibrium and dynamic surface tension of water-based compositions.
EP 0 930 346 corresponding to U.S. application Ser. No. 09/009,099 filed Jan. 20, 1998 discloses the use of N,N'-dialkyl alkylenediamines for reducing equilibrium and dynamic surface tension of water-based compositions.
There are few references describing low foam surfactants in developer compositions. JP 10-319606 discloses that commercially available ethylene oxide (EO)/propylene oxide (PO) block polymers give good wetting and low foam.
JP 03-062034 discloses polyoxyalkylene dimethyl polysiloxanes as good surfactants with low foam in developer formulations. Polysiloxanes are known to rearrange or decompose under conditions of high pH.
Although there are a few references to the use of amines in photoresist developer compositions, they are not related to the use of surface active agents. U.S. Pat. No. 5,252,436 discloses the use of relatively high levels of amine additives (3-30 wt %) and U.S. Pat. No. 5,039,595 uses amine additives at levels of 5-50 wt %. Both of these disclosures appear to be using the amines to alter the bulk solvent properties of the developer solution.
U.S. Pat. No. 4,997,748 discloses cyclic nitrogen compounds at levels of 0.1 to 10 wt % to decrease scum formation and enhance image sharpness during photoresist development. Among the cyclic nitrogen compounds taught is the cyclic urea 1,3-dimethyl-2-imidazolidinone. Since the nitrogen compounds are not amphipathic, it is not likely that they will lower surface tensions at low concentrations, and their utility appears to be based on properties other than surface tension reduction. 1,3-dimethyl-2-imidazolidinone is well known as a very good solvent and not as a surface-active material.
U.S. Pat. No. 4,828,965 discloses the use of lower alkanolamines (1-4 carbons) in combination with alcohols at concentrations of 0.40-5 wt %.
U.S. Pat. No. 4,741,989 discloses the use of small amounts of amines to modify the reaction chemistry of the quinonediazide photoactive compounds in photoresists, but only small chain amines are used and no surface active amines are cited.
U.S. Pat. No. 4,628,023 discloses water soluble amines as the alkali source for developer solutions. Because the preferred pH range is above 12.5, the use of organic amines would necessarily be at high concentrations.
JP 61-179651 discloses the use of amine-containing developer solutions with surface tensions of between 25 and 50 dyne/cm. These surface tensions are achieved by the use of relatively large amounts of non-surface-active amines (3-5 wt %) in combination with tetramethylammonium hydroxide as the base.